Increasing competition for fossil fuels, and the need to avoid release of carbon dioxide from combustion of these fuels requires that we develop new and sustainable approaches for energy production. Microbial fuel cells (MFCs) provide a new method for renewable electricity production from the degradation of organic matter.
Microbial electrolysis cells (MECs) represent another technology that makes use of electrogenic bacteria for wastewater treatment. In an MEC hydrogen gas can be produced by a process called electrohydrogenesis. Hydrogen gas generation is not spontaneous, however, as the voltage produced by the anode using a substrate such as acetate (EAn≅−0.2 V in practice) is insufficient for that needed to evolve hydrogen gas the cathode (Ecell=−0.414 V, pH=7). By adding a small voltage of >0.2 V, however, MECs can produce hydrogen gas at very high energy efficiencies of 200-400 percent based on electrical energy alone, or 82 percent based on both electrical energy and heat of combustion energies for the substrate.
Despite promising developments, there is a continuing need for methods and systems for sustainable production of fuels and for carbon capture.